In order to avoid the boundary effect, the entanglement \(C_{30,31}\) 
of the central two qubits is plotted as a function of the time \(t\) 
for different anisotropic interaction in Fig. 2. The anisotropic
interaction has little influence on the height of the first peak of
the entanglement. When \(J_z=0, 0.5\) , the entanglement drops down to
zero after reaching the peak. The entanglement cannot generate at
any longer time. When \(J_z=1.0\) , the entanglement can appear and
disappear alternatively. When \(J_z=1.5, 2.0\) , the entanglement can
create, oscillate and does not disappear for longer time. Except the
first peak in \(C_{30,31}\) , the height of oscillation of entanglement
with \(J_z=2.0\)  is higher than that with \(J_z=1.0, 1.5\) . This is due
to the strong dependence of the damping coefficient of the
entanglement wave on the anisotropic parameter. When \(t\)  increases,
the relative height of the first peak and the average value of
\(C_{30, 31}\)  becomes smaller with increasing \(J_z\) . The increase of
\(J_z\)  reduces the relative height in \(C_{30, 31}\) 
[1]}, [2]}.
